Unreachable case in two-level sealed hierarchy is not detected

[smarter]

Given the following code:

sealed trait Foo[A]
case class One[A]() extends Foo[A]
sealed abstract case class Bar[A]() extends Foo[A]
class Two() extends Bar[String]

object Test {
  def test(x: Foo[Int]) = x match {
    case One() =>
  }
}

The exhaustiveness checker is smart enough to not warn, because no instance of Bar is a subtype of Foo[Int].

However, if we add a case for Bar() like this:

sealed trait Foo[A]
case class One[A]() extends Foo[A]
sealed abstract case class Bar[A]() extends Foo[A]
class Two() extends Bar[String]

object Test {
  def test(x: Foo[Int]) = x match {
    case One() =>
    case Bar() =>
  }
}

We should get an unreachable code warning (and indeed, scalac produces one), but we don't.

[smarter]

Related, but maybe a different issue, in the following code:

trait Foo[A]
case class One() extends Foo[String]

object Test {
  def test(x: Foo[Int]) = x match {
    case One() =>
  }
}

We get an error with scalac but nothing in Dotty:

try/pattern-no-instance.scala:6: error: constructor cannot be instantiated to expected type;
 found   : One
 required: Foo[Int]
    case One() =>
         ^
one error found